The midsagittal cross-sectional dimensions of the corpus callosum, the coronal cross-sectional area of the lateral ventricles at the level of the pons, and a three-dimensional estimate of intracranial volume were derived from magnetic resonance brain images obtained from 45 monozygotic and 40 dizygotic male twin pairs aged 68 to 78. Univariate genetic analyses indicated strong genetic influences contributing significantly to the variability of each brain structure. The estimated proportion of genetic variance (i.e. heritability) was 81% for intracranial volume, 79% for the midline cross-sectional area of the corpus callosum, and 79% for lateral ventricle size. There was no evidence that shared environmental influences contributed significantly to twin-pair similarities. We further used bivariate genetic modeling to estimate the genetic and environmental correlation between correlated brain structures. Intracranial volume and corpus callosum area was highly correlated, and this relationship was entirely due to shared genetic effects between these two brain structures. By contrast, the relationship between the height of the corpus callosum and the size of the lateral ventricles was due to both genetic and environmental influences in common. Corresponding genetic and environmental correlations were 0.68 and 0.58, respectively, indicating that more than half of the genetic and environmental influences on these two brain structures were shared. The manner in which the brain responds to the environment with advancing age is highly genetically determined, both for the lateral ventricles, which dilate with aging and disease, and for the corpus callosum, which is deformed in shape by age-related ventricular enlargement, whereas its midline cross-sectional area remains unchanged.

Aged↗

PubMedDate not supplied

Genetic influences and grip strength norms in the NHLBI twin study males aged 59-69.

Maximal grip strength was measured in kilograms using a hand dynamometer on 344 unrelated males between the ages of 59 and 70 participating in the third examination of the NHLBI Twin Study. There was a significant linear decline in mean grip strength over this age range. Mean grip strength and grip strength per kilogram weight are presented for age 59, ages 60-64 and 65-69. Genetic analysis using 127 pairs of identical (MZ) twins and 130 pairs of fraternal (DZ) twins indicated significant genetic effects for absolute grip strength and grip strength per kilogram weight. The largest estimate of heritability (65%) was obtained for grip strength adjusted for significant effects of weight, height, age, and various anthropometric measures of fatness, muscle mass, and frame size.

Age Factors↗

PubMedDate not supplied

Spouse-pair similarity on the California Psychological Inventory with reference to husband's coronary heart disease.

The present article reports on the results of several comparisons between 45 adult males with diagnosed coronary heart disease (cases) and their wives and 50 adult males without coronary heart disease (noncases) and their wives recruited from the Western Collaborative Group Study. The California Psychological Inventory and a life satisfaction inventory were administered to the couples in the two types of families. Results indicate that although both sets of husbands and wives fell within the well-functioning range on the CPI, wives of cases were significantly more dominant and less flexible than wives of noncase husbands. Case husbands were significantly more dominant than noncase husbands. No mean differences existed between case and noncase husbands and wives on a variety of life satisfaction measures. Computation of spouse-pair correlations revealed a pattern of overall dissimilarity across the CPI scales for case couples and overall similarity for the noncase couples. The only scale on which case spouse pairs were significantly similar was one measuring depression. Noncase couples were significantly more similar than case couples on scales measuring sociability, self-acceptance, and socialization. Previous findings from the research literature in the fields of personality, cardiac rehabilitation, and assortative mating are used to generate three competing hypotheses relating the present findings to cross spouse disease associations.

Achievement↗

PubMedDate not supplied

The Cook and Medley HO scale: a heritability analysis in adult male twins.

Thirty-seven pairs of monozygotic (MZ) and 60 pairs of dizygotic (DZ) middle-aged, male, American twins were studied to determine the heritability of the Cook and Medley Hostility (HO) scale and its two subscales, Cynicism and Paranoid Alienation. No clear evidence for a significant genetic component was indicated for the full HO scale and the Paranoid Alienation subscale. Scores on these scales were found to be associated with age, socioeconomic status, the twinning condition, and the Minnesota Multiphasic Personality Inventory (MMPI) K scale. DZ twins scored higher than MZ on HO and Cynicism, and lower on the MMPI K scale. Statistical adjustments for age and socioeconomic status removed twin mean differences and weakened MZ intrapair correlations on the HO scale but did not change overall conclusions regarding heritability. After the association with K was partialled out from these scales and retested for heritability, both HO and Paranoid Alienation showed a weaker twin pair similarity than that observed in the unadjusted scales. However, Cynicism, the scale with the greatest item overlap with the K scale, was not affected by the adjustment. Since no genetic component was evident for the K scale in this sample it was concluded that if a genetic influence in these MMPI scales is present, it is mostly in the Cynicism subscale of HO.

Adult↗

PubMedDate not supplied

Relationship of family history scores for stroke and hypertension to quantitative measures of white-matter hyperintensities and stroke volume in elderly males.

White-matter hyperintensities (WMHI) are frequently associated with cerebrovascular risk factors in the elderly, particularly hypertension, and have been interpreted as a subclinical form of ischemic brain damage. WMHI, clinical stroke and blood pressures show significant genetic influences. The objective of this study was to determine whether a relationship exists between family history of stroke and/or hypertension in first degree relatives and WMHI in the elderly. WMHI and stroke (CVA) volumes were quantified from brain MRI performed on 414 white, male twins born between 1917 and 1927 (average age 72.3 +/- 2.9 years). WMHI, adjusted for age and head size, was significantly correlated with the family history score (r = 0.21, p < 0.001). Dividing the family history scores into quintiles revealed significant differences in WMHI by quintile mean (p < 0.05). Subjects in the highest quintile of family history score had the highest mean WMHI. Recalculation of the family history score, by only counting relatives reported to have had a clinical stroke as a positive event, revealed a nonsignificant correlation with WMHI, but the correlation of the family history score with MRI CVA volume was significant (p < 0.05). Stepwise multivariate analysis including ApoE status, current smoking status, smoking packyear history, Doppler ankle/arm blood pressure ratios, current and long term hypertensive status and current systolic and diastolic pressures indicated that the stroke/hypertension family history score was the single best predictor (p < 0.01) of WMHI volumes. Family history was not an independent predictor of CVA volume.

Aged↗

PubMedDate not supplied

High density lipoprotein cholesterol. A 16-year longitudinal study in aging male twins.

The National Heart, Lung, and Blood Institute Twin Study is a collaborative, longitudinal study of white, male twins who were veterans of World War II and were born between 1917 and 1927. The twins were selected from the National Academy of Sciences/National Research Council Twin Panel and were examined three times (1969-73, 1981-82, and 1986-87). At all three exams, the dizygotic (DZ) twins were found to have a greater total variance for high density lipoprotein cholesterol (HDL-C) than the monozygotic (MZ) twins (p less than 0.05). DZ variance estimates were also larger than the variance of singletons from the second National Health and Nutrition Examination Survey. At the third exam, HDL-C was divided by precipitation into HDL2 and HDL3 fractions, and HDL2 was found to be the primary cause of the greater DZ total variance (DZ/MZ HDL2 variance = 2.22). The DZ/MZ variance ratio decreased 9% after adjustment of HDL2 for correlations with plasma triglycerides, alcohol consumption, smoking, exercise, and body mass index measured at the third exam. Postulated causes of the difference between MZ and DZ total variances include World War II induction screening, environmental influences unique to one zygosity, and genetic factors related to twinning. Further understanding of the etiology of this striking difference between MZ and DZ twin variance for HDL-C fractions could lead to more effective methods of decreasing the complications of arteriosclerosis.

Adult↗